In the related art, an erroneous input of a numerical value such as a price or a numerical quantity in electronic trading causes problems. For example, there is the problem that a bidder erroneously inputs a price more than an originally intended price as a bid price in a net auction (online auction), or that a retailer erroneously inputs an order amount (the number of the ordered products) more than an originally intended order amount as an order amount at the time of ordering products from a wholesaler. Besides the electronic trading, there are many chances of inputting numerical values to an information processing device in information processing society. For this reason, in many cases, an erroneous numerical value input causes big economic loss and credit loss.
In order to resolve the above problem, Patent Document 1 (paragraphs [0048] to [0053], and FIG. 7) describes a technology for multiplying an input value of an “amount of money” by an input value of a “numerical quantity” and giving an inputter warning of the possibility of a numerical value being erroneously input, when the calculation result is more than a predetermined limitation value.